1. Field of the Invention
The present invention relates to a steering column apparatus, more particularly to a steering column apparatus to be employed for a vehicle provided with a telescopic mechanism and a tilting mechanism.
2. Description of Related Art
Both of the telescopic mechanism and the tilting mechanism are used to adjust the position in the front-rear direction and the tilting angle of the steering wheel of a subject car appropriately to the figure and comfort of the driver, thereby making it easier for the driver to drive the car.
Each of the telescopic mechanism and the tilting mechanism is provided with a clamp/unclamp mechanism so as to adjust the position in the front-rear direction and the tilting angle of the steering wheel as described above. When in such an adjustment, the clamp/unclamp mechanisms of the telescopic mechanism and the tilting mechanism are unclamped once to adjust the front-rear direction/tilting angle in that state, then the mechanisms are clamped again after completing the adjustment.
The telescopic mechanism is processed and built in the subject steering column apparatus accurately enough so that when it is to be clamped/unclamped, it receives a proper pre-load and is fit properly in the device, thereby preventing its moving parts from excessive play. Consequently, the telescopic mechanism comes to need an operation force larger than that of the tilting mechanism. The driver is thus required to use both of his/her hands to operate the steering wheel to adjust the position of the steering wheel in the front-rear direction. This has been a problem of the conventional technique. The published GB patent No.2281375 discloses a steering column apparatus provided with a single operation handle that can be operated by the driver with his/her hand on the steering wheel.
In the steering column apparatus disclosed by the above published GB patent No.2281375, the operation handle is usually kept pulled by a pulling spring so that the operation handle stays at its refuge position that is apart from the steering wheel. The driver is thus prevented from touching the operation handle by accident while driving the car. When adjusting the steering wheel, the operation handle is pulled toward the steering wheel resisting the force of the pulling spring. This movement of the operation handle is transmitted to the clamp device provided apart from the operation handle and used for adjusting the steering wheel in the front-rear direction through a cable movable in a flexible tube, thereby the clamp device is unclamped. And, this movement of the operation handle unclamps the clamp device provided near the operation handle and used for adjusting the tilting angle of the steering wheel. After completing the adjustments of the position in the front-rear direction and the tilting angle of the steering wheel by operating the steering wheel with both hands while putting his/her fingers on the operation handle, if the driver takes the fingers off the operation handle, the operation handle is pulled by the pulling spring to return to the refuge position, then both of the clamp devices for adjusting the position in the front-rear direction and the tilting angle of the steering angle are clamped.
The steering column apparatus disclosed by the above published GB patent needs a mechanism for moving the operation handle between the refuge position and a position at the steering wheel side, as well as a complicated mechanism for keeping the operation handle at the refuge position. In addition, both cable and its tube are flexible enough to be able to minimize the curvature so that the cable/tube can be moved freely in the entire adjustment range of the steering wheel. Consequently, part of the cable/tube is protruded from the steering column apparatus. This is not only unbecoming, but also might cause troubles. This is why the transmission mechanism having such cable and tube comes to injure the device reliability. And, the flexible cable seems to degrade the operability of the steering column apparatus itself, as well.
The mechanisms for adjusting the position in the front-rear direction and the tilting angle of the steering wheel are used not only when in driving, but also when getting in/out of the car. This is to make it easier for the driver to get in/out of the car; the driver just moves the steering wheel to its refuge position at that time. If the steering wheel is to be moved to its refuge position only to get in/out of the car such way, what the driver needs to do at that time is just push the steering wheel to the other side using the tilting mechanism. In the steering column apparatus disclosed by the above published GB patent, however, both of the tilting mechanism and the telescopic mechanism must be unclamped together by an operation of the operation handle when in an adjustment of the position of the steering wheel as described above. Consequently, the driver must put out his/her strength to operate the operation handle. In addition, the unclamped telescopic mechanism moves easily. If it moves, it must be adjusted again before starting another drive.